1. Field of the Invention
The present invention relates to a rewritable information recording medium, and more particularly to an information recording medium to which distributed music content (music) is recorded. The present invention also relates to an information recording apparatus for recording distributed music content to such an information recording medium, a reproducing apparatus for reproducing recorded music content from the information recording medium, and a copying apparatus.
2. Description of the Related Art
In recent years, with the result that various compression encoding methods were invented and technologies related to the internet rapidly came into wide use, a number of electronic music distribution systems have been offering music distribution services. In such systems, compression encoding methods, such as MP3, are utilized to allow music to be distributed to a user in a short amount of time even if a narrow-band network is used. In the present specification, data including distributed music is referred to as “EMD (electronic music distribution) data”. Most of such electronic music distribution systems presuppose the use of a PC (personal computer), and therefore reproduction compatibility, i.e., distributed music can be reproduced by any PC, is not a major problem. As a result, a large number of electronic music distribution systems are currently in service, and there are differences in format for the EMD data among the electronic music distribution systems.
Further, in many cases, the electronic music distribution system employs a copy control method which is different from a conventional copy control method. The conventional copy control method is of a generation management type, which allows an original medium to be copied but is controlled such that a grandchild copy of the original medium cannot be created. As methods for realizing such copy control, there are SCMS (serial copy management system) for use with a CD (compact disc) or an MD (MiniDisc), CPPM (content protection for prerecorded media) for use with DVD (digital versatile disc) Audio, and the like. On the other hand, in many cases, the electronic music distribution system employs methods, such as “MOVE”, “CHECK OUT/IN”, and the like. The “MOVE” method is used to copy contents of an original medium to another medium, and the contents of the original medium are deleted upon completion of copying. Moreover, in many cases, contents of a target medium, which are created by copying, are also allowed to be “MOVED”, as contents of an original medium, to another medium.
In an original medium which is in conformity with the “CHECK OUT” method, counter information is recorded together with contents thereof. When copying the contents of the original medium to another medium, the counter information is modified simultaneously with copying the contents. When the value of the counter amounts to a prescribed number, additional copying of the original medium is not allowed. Moreover, a grandchild copy is not allowed to be created from a target medium to which the contents of the original medium are recorded. The “CHECK IN” method is used in a manner opposite to the “CHECK OUT” method. That is, counter information recorded in an original medium is updated simultaneously with deleting contents of a target medium, which are copied from the original medium in accordance with the “CHECK OUT” method. This allows the contents of the original medium to be copied to another medium. With regard to such copying, most of the current electronic music distribution systems also presuppose the use of a PC, and therefore the fact that any PC can make a copy of distributed music content does not cause any major problems.
Since most of the current electronic music distribution systems presuppose the use of a PC, any user who does not have a PC cannot receive electronic music distribution services. Therefore, there is a need for consumer apparatuses which can be readily handled by a large number of users and can record/reproduce EMD data to/from an information recording medium (disc). For example, a case where a household audio recorder/player, which is in conformity with DVD-RAM standards, is used for recording/reproducing EMD data to/from a DVD-RAM disc is considered. In this case, there are necessities for a data format and an information recording apparatus which allow conversion of distributed EMD data into LPCM (linear pulse code modulation) audio data or audio data processed by other compression coding methods, recording of the converted audio data to a DVD-RAM disc, and the use of new copy control methods, such as “MOVE”, “CHECK OUT”, and the like. Moreover, it is necessary to realize reproduction compatibility which allows audio data recorded in a disc to be reproduced by any reproducing apparatus, long-time recording which allows data to be recorded as much as possible, and high-speed copying performed by any copying apparatus in accordance with a “MOVE” or “CHECK OUT” method.
It is conceivable that a method which realizes such reproduction compatibility, long-time recording, and high-speed copying, uses a mandatory compression encoding method defined as a disc standard. Where the mandatory compression encoding method is defined as a disc standard, audio data is always required to be recorded to a disc by such a compression encoding method, so as to ensure reproduction compatibility with any reproducing apparatus. Moreover, when audio data is recorded to a disc by a compression encoding method, it is possible to realize long-time recording and high-speed-copying. However, when a mandatory compression encoding method is defined as a disc standard, any apparatus, which is in conformity with such a standard, is always required to mount a decoder, which uses the mandatory compression encoding method, and there is an obligation to pay a license fee. Moreover, even if any new high sound-quality and high compression-rate encoding method is developed in the future with the advance of technology, data recording has to be performed using a conventional mandatory compression encoding method.
Further, in the case of copying music data for use in one application program, which uses a mandatory compression method, in order to use the music data in another application program, if the mandatory compression encoding method is different from a compression encoding method supported by the target application program in which the copied music data is used, the copied music data is required to be converted so as to conform to the compression encoding method supported by the target application program. As a result, high-speed copying cannot be realized and even deterioration in sound quality is caused by such conversion. In this manner, various problems are caused by defining the mandatory compression encoding method as a disc standard.
In order to realize reproduction compatibility, long-time recording, and high-speed copying while avoiding the problems as described above, it is conceivable to define a mechanism which allows a user to choose whether to record LPCM audio data created by decoding the original audio data, which is encoded by a specific compression encoding method, so as to ensure reproduction compatibility, or to record the original audio data without converting the format therefor so as to realize long-time recording and high-speed copying. Alternatively, in some cases, music data encoded by both an LPCM encoding method and a specific compression-encoding method are recorded to a disc. In such a case, any one of the following data formats (1), (2), and (3) is required.
(1) Data format with music data which ensures reproduction compatibility.
Unlike a PC, it is difficult for a household audio player to be compatible with all of a large number of electronic music distribution systems. Therefore, by defining an audio data reproducing means, which is necessarily mounted on all audio players, and recording audio data in conformity with a specific encoding method which can be reproduced using such an audio data reproducing means, reproduction compatibility is ensured. In this case, LPCM is desirable as the specific encoding method.
(2) Data format with compressed audio data included in EMD data, which can be copied from one disc to another disc at high speed using any copying apparatus.
In order to perform a “Move” operation or a “CHECK OUT” operation on EMD data distributed by an electronic music distribution system, the format for the EMD data is required to be decoded, and therefore it is difficult for a household audio apparatus to be compatible with all electronic music distribution systems. Therefore, by defining an audio data copying means, which is necessarily mounted on all copying apparatuses, and recording compressed music data, which can be copied at high speed using such an audio copping means, to a disc, it is ensured that the EMD data can be copied at high speed using any copying apparatus.
(3) Data format with a mechanism which realizes long-time recording.
Specifically, the mechanism provides a choice between recording of both the audio data specified by (1) and the compressed audio data specified by (2) and recording of only the compressed audio data specified by (2). Alternatively, only the compressed audio data specified by (2) is recorded without any choice. When simultaneously recording the audio data specified by both (1) and (2), reproduction compatibility can be ensured but long-time recording cannot be realized. On the other hand, when recording only the compressed audio data specified by (2), long-time recording can be realized but reproduction compatibility is not ensured. Therefore, the compressed audio data specified by (2) can be reproduced only by a player having a reproducing means which can reproduce the compressed audio data.
As described above, when both the audio data specified by (1) and the compressed audio data specified by (2) are recorded in an information recording medium for the same piece of music, in the light of convenience for a user, it is desirable that either one of the audio data specified by (1) and (2) is used for reproduction or copying. Prior art documents, e.g., Japanese Laid-Open Patent publication No. 11-120748, disclose reproducing apparatuses for reproducing audio data according to reproduction environment, i.e., according to their ability to receive a data stream. However, such reproducing apparatuses cannot choose either the audio data specified by (1) or the compressed audio data specified by (2) for reproduction.
An objective of the present invention are to provide an information recording medium in which data is recorded using a disc format which solves the above-described problems, and the other objectives of the present invention are to provide an information recording apparatus, an information reproducing apparatus, and a copying apparatus, which are used with such an information recording medium.